Modulation of hepatic inflammation and energy-sensing pathways in the rat liver by high-fructose diet and chronic stress

Purpose High-fructose consumption and chronic stress are both associated with metabolic inflammation and insulin resistance. Recently, disturbed activity of energy sensor AMP-activated protein kinase (AMPK) was recognized as mediator between nutrient-induced stress and inflammation. Thus, we analyzed the effects of high-fructose diet, alone or in combination with chronic stress, on glucose homeostasis, inflammation and expression of energy sensing proteins in the rat liver. Methods In male Wistar rats exposed to 9-week 20% fructose diet and/or 4-week chronic unpredictable stress we measured plasma and hepatic corticosterone level, indicators of glucose homeostasis and lipid metabolism, hepatic inflammation (pro- and anti-inflammatory cytokine levels, Toll-like receptor 4, NLRP3, activation of NF kappa B, JNK and ERK pathways) and levels of energy-sensing proteins AMPK, SIRT1 and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1 alpha). Results High-fructose diet led to glucose intolerance, activation of NF kappa B and JNK pathways and increased intrahepatic IL-1 beta, TNF alpha and inhibitory phosphorylation of insulin receptor substrate 1 on Ser(307). It also decreased phospho-AMPK/AMPK ratio and increased SIRT1 expression. Stress alone increased plasma and hepatic corticosterone but did not influence glucose tolerance, nor hepatic inflammatory or energy-sensing proteins. After the combined treatment, hepatic corticosterone was increased, glucose tolerance remained preserved, while hepatic inflammation was partially prevented despite decreased AMPK activity. Conclusion High-fructose diet resulted in glucose intolerance, hepatic inflammation, decreased AMPK activity and reduced insulin sensitivity. Chronic stress alone did not exert such effects, but when applied together with high-fructose diet it could partially prevent fructose-induced inflammation, presumably due to increased hepatic glucocorticoids

Analysis of essential oils through comprehensive two-dimensional gas chromatography: General utility

The first description of a comprehensive two‐dimensional gas chromatography (GC×GC) elucidation of an essential oil appeared in 2000 (J. High Resol. Chromatogr. 2000;23:208‐214); since then, a variety of investigations have been published also involving complex samples related to essential oils, such as perfumes. In many instances, there was no mismatch between the use of GC×GC, and the analytical scope; on the other hand, in some specific cases the use of GC×GC appeared to be less adequate. The present contribution is focused on the application of GC×GC, within the context of essential oil analysis. Perfumes are also tightly related to essential oils, and so are herein considered. Rather than to describe and critically‐review all the research related to such investigations, attention has been devoted to the general analytical usefulness of GC×GC in the aforementioned application fields, over more established approaches, such as conventional GC and heart‐cutting multidimensional GC

Modulators for comprehensive two-dimensional gas chromatography

The analytical benefits of comprehensive two-dimensional gas chromatography (GC × GC) methods have been exploited and emphasized in the past two decades. The unexpectedly complex nature of many real-world samples amenable to GC analysis has been elucidated through the enhanced resolving power of GC × GC. Simple but fundamental devices, called modulators, enable continuous heart-cutting and re-injection, without which GC × GC analysis cannot be achieved. The present review focuses on the history (1991-2010), and present trends and future prospects for GC × GC modulation. We provide detailed descriptions and set out the advantages and the disadvantages of the most significant thermal and pneumatic modulators. © 2011 Elsevier Ltd

Comprehensive two-dimensional gas chromatography-mass spectrometry: Recent evolution and current trends

The present contribution is focused on the evolution and current trends of comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS), with respect to a review that described this specific methodology published at the beginning of 2008 (Mondello et al., 2008). In fact, since then there has been considerable evolution in the MS field, certainly exceeding that observed in GC × GC. In particular, the present paper will cover the combination of novel MS machines [single quadrupole (Q) and triple quadrupole, isotope ratio, low- and high-resolution time-of-flight (ToF), hybrid (Q-ToF)] to GC × GC systems, and will position comprehensive two-dimensional gas chromatography within the wider context of separation science

A flow-modulated comprehensive gas chromatography–mass spectrometry method for the analysis of fatty acid profiles in marine and biological samples

The present investigation is focused on the development of a flow-modulator (FM) comprehensive 2D GC (GC×GC)-quadrupole mass spectrometry (qMS) approach, for the analysis of fatty acids. A recently developed flow modulator interfaced an apolar–polar column set, and was used for the first time with a mass spectrometer. Method development was achieved by using a standard mixture, containing fatty acid methyl esters (FAMEs). The total run time was approx. 40 min, thus relatively rapid. The optimized FM GC×GC–qMS method was applied to marine and biological FAMEs. Validation parameters such as intraday and inter-day repeatability, limits of identification (mass spectral quality was evaluated at various FAME concentrations), and quantification were measured. Peak assignment was performed using pure standard compounds (when available), linear retention indices (LRIs), a dedicated FAME MS database, and specific bidimensional chromatogram positions. The MS database contained one-dimensional LRI information, exploited as a filter during the MS database search procedure. A good agreement was observed between database LRI values, and those calculated on the twin-column set. The FM GC×GC–qMS method can be considered as a valid counterpart, with respect to cryogenically modulated GC×GC, in the fatty acid field of research

Flow modulation comprehensive two-dimensional gas chromatography-mass spectrometry using ≈ 4 mL min-1 gas flows

The main objective of the herein described research was focused on performing satisfactory flow modulation (FM), in comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS), using an MS-compatible second-dimension gas flow of approx. 4 mL min-1. The FM model used was based on that initially proposed by Seeley et al. [3]. The use of limited gas flows was enabled through fine tuning of the FM parameters, in particular the duration of the re-injection (or flushing) process. Specifically, the application of a long re-injection period (i.e., 700 ms) enabled efficient accumulation-loop flushing with gas flows of about 4 mL min-1. It was possible to apply such extended re-injection periods by using different restrictor lengths in the connections linking the modulator to the auxiliary pressure source. FM GC × GC-MS applications were performed on a mixture containing C9-10 alkanes, and on a sample of essential oil. GC × GC-MS sensitivity was compared with that attained by using conventional GC-MS analysis, in essential oil applications. It was observed that signal intensities were, in general, considerably higher in the FM GC × GC-MS experiments